1. Field of the Invention
The present invention relates to a light source device having a plurality of lighting regions which are controllable independently of one another, a light source driving device and a light emission amount control device applied to such a light source device, and a liquid crystal display using such a light source device.
2. Description of the Related Art
In recent years, flat panel displays as typified by liquid crystal TVs and plasma display panels (PDPs) have become a trend, and among them, most of mobile displays are liquid crystal displays, and precise color reproducibility is desired in the mobile displays. Moreover, as backlights for liquid crystal panels, CCFLs (Cold Cathode Fluorescent Lamps) using fluorescent tubes are mainstream; however, mercury-free light sources are environmentally desired, so light emitting diodes (LEDs) and the like hold promise as light sources replacing CCFLs.
In such an LED backlight system, to improve video response of a liquid crystal panel, a light source section includes a plurality of separate lighting sections so as to approximate the impulse-type drive of a CRT (Cathode Ray Tube), thereby the light source section carries out sequential lighting operation (blinking operation) in which the plurality of lighting sections are sequentially turned on on a horizontal line basis. It is considered that compared to a CCFL backlight system, the LED backlight system is suitable for the sequential lighting operation, because the LED backlight system has good response when switching between a lighting-on state and a lighting-off state, and the LED backlight system does not have afterglow characteristics.
Further, in the LED backlight system, when a light-sensing device detects illumination light, and the light emission amount of the LED is controlled by a detected value, fluctuations in the intensity of illumination light can be reduced. In addition, in the case of an additive process backlight system which uses a plurality kinds of LEDs such as a red LED, a green LED and a blue LED to obtain a specific color light by mixing a plurality of color lights, in addition to fluctuations in the intensity of illumination light, fluctuations in the chromaticity of illumination light can be reduced by the same feedback system.
For example, Japanese Unexamined Patent Application Publication No. 2005-208486 discloses a technique in which when the LED backlight system performs sequential lighting operation (in this case, sequential light-off), the light emission amount of each LED group (each lighting section) is controlled based on information of the light amount variations detected by a photosensor section.